Power on reset circuit
AssigneeKabushiki Kaisha Toshiba
InventorMasahiro Ikezaki
Life of this patent
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Abstract
A power on reset circuit includes a charge and discharge circuit for performing charge or discharge operation on the basis of a potential obtained by dividing a power supply voltage using a potential divider circuit. The potential thus outputted is held by a first latch circuit to output a reset on signal or a reset off signal. The output state of the charge and discharge circuit is inverted to the power supply voltage on the basis of the output potential of the first latch circuit using a second latch circuit, which comprises the minimum number of elements including a NAND gate, an inverter and two capacitors. Thus, the power on reset circuit can obtain a stable reset signal if the initial state of the reset signal output is in either the power supply voltage level or the ground level.
Claims11
A power on reset circuit comprising:
- a first switch circuit arranged between a power supply voltage terminal and a first node;
- a second switch circuit arranged between the power supply voltage terminal and a second node;
- a potential dividing circuit, arranged between said first node and a ground terminal, for outputting a potential obtained by dividing a potential of said first node;
- a charge and discharge circuit, arranged between said second node and the ground terminal, for charging or discharging said second node in accordance with an output potential of said potential dividing circuit;
- a first latch circuit for holding a potential of said second node to output a signal from an output terminal to said first switch circuit to control a switching operation of said first switch circuit;
- and
- a second latch circuit for receiving an output signal of said first latch circuit to control a switching operation of said second switch circuit,
- wherein an input side of said first latch circuit is electrically connected to the power supply voltage terminal when an output side potential of said first latch circuit follows a rise of said power supply voltage in an initial state in which the power supply is turned on.
A power on reset circuit for producing a reset signal when a power supply is turned on, said power on reset circuit comprising:
- a first switch circuit arranged between a power supply voltage terminal and a first node;
- a second switch circuit arranged between the power supply voltage terminal and a second node;
- a potential dividing circuit, arranged between said first node and an ground terminal, for outputting a potential obtained by dividing a potential of said first node;
- a charge and discharge circuit, arranged between said second node and the ground terminal, for charging or discharging said second node in accordance with an output potential of said potential dividing circuit;
- a first latch circuit for holding a potential of said second node to output a signal from an output terminal to said first switch circuit to control a switching operation of said first switch circuit;
- and
- a second latch circuit for receiving an output signal of said first latch circuit to control a switching operation of said second switch circuit,
- said second latch circuit including:
- a NAND gate having a first input terminal connected to said output terminal and an output terminal connected to a control terminal of said second switch circuit;
- an inverter having an input terminal connected to said output terminal of said NAND gate and an output terminal connected to a second input terminal of said NAND gate;
- a first coupling capacitor connected between the power supply voltage terminal and said second input terminal of said NAND gate;
- and a second coupling capacitor connected between said output terminal of said NAND gate and the ground terminal.
Dependencies are inferred from the claim text.